These studies will examine the adult structure and function of the macaque monkey striate visual cortex. The origins, cortical distribution patterns and physiological properties of different geniculo-cortical fiber populations will be investigated anatomically and physiologically. These studies will provide essential information concerning the input matrices from which the properties unique to visual cortex are then evolved. We will also explore the physiological properties of cortical neurons receiving these different geniculate fiber populations and the anatomical organization of their intrinsic axon relays within striate cortex. We hope in addition to provide more precise anatomical and physiological information concerning spatially ordered response patterns in populations of cortical neurons. Inhibitory circuits in the cortical neuropil will be explored using immunocytochemical means to identify the presence of glutamic acid decarboxylase (GAD), the synthetic enzyme for the inhibitory neuro-transmitter gamma-aminobutyric acid (GABA). Finally, the tree shrew visual cortex will be used as a model system to explore the nature and development of striate cortex intrinsic periodic lattice connections and the ordering of striate to prestriate projections. These approaches should improve our understanding of this crucial region of the primate visual system. The results should illustrate general principles that will be broadly applicable to other regions of the cerebral cortex and to the human nervous system.